GM first released the Gen-III 5.3L truck V-8 in 1999 in the Silverado and Sierra truck platforms. GM Performance Parts (GMPP) has taken notice of the millions of these and the 4.8L V-8s that have been placed into '99-'05 trucks and SUVs, and released a bolt-in performance replacement—the LS327. Producing 327 hp and 347 lb-ft of torque, the new LS327 can wake up your tired, high-mileage 4.8 or 5.3L and add a whole new level of performance to your daily driver. Not just a relabeled LS-engine, GMPP did some upgrades to the engine by inserting eight Grafal coated hypereutectic pistons and a snappier camshaft with 0.467/0.479 lift and 196/201 duration. The LS327/5.3L HO, comes as a long-block, complete with valve covers, and is compatible with truck and SUV engine accessories. Each GMPP crate engine undergoes 50 hours of high-load durability testing, comes with a 24 month warranty, and with a price tag of only $3,150, you can’t go wrong.
Taking a look at our truck fleet, the '02 Chevy Avalanche stuck out like a sore thumb because of its high-mileage, seemingly worn-out 5.3L under the hood. Calling up GMPP, we placed an order for the new LS327 and lined up a shop to help us with the engine swap. Before we took delivery of the crate engine, we performed a chassis dyno test at the Source Interlink Tech Center. Jason Scudellari, the Mustang chassis dyno technician, made three strong pulls on the dyno to give us an original engine performance baseline. Surprising to all of us, the Avalanche, equipped with 22-inch wheels/tires, a K&N intake, and Magnaflow exhaust, only made 202 hp and 272 lb-ft of torque. Rated at 285 hp (at the flywheel) in '02, that's a loss of 83 ponies over the last 120,736 miles. Scratching our heads, we couldn't wait for the new GMPP LS327 to be dropped off.
The new GMPP crate engine LS327 was loaded into the bed of the '02 Avalanche and delivered to Trader's Sport Truck in Santa Fe Springs, California, for the engine swap.
We photographed the engine swap procedure starting with the removal of the factory 5.3L Vortec that survived 120,736 miles. Some of the original engine external components and accessories were reused on the new LS327 crate engine.
The '02 Avalanche was tied down to the Mustang Dyno at the Source Interlink tech center fo
The (GM Performance Parts) LS327/5.3L HO crate engine was shipped in a protective wooden c
After the Avalanche was mounted on the hoist, Ox Higgins, of Trader’s Sport Truck, in Sant
The original exhaust manifolds were unbolted and removed from the cylinder heads.
Next up, the fan shroud was removed from the radiator before removing the fan from the wat
Fuel injection wire harnesses were then disconnected from the fuel injectors and the coil
After removing the serpentine belt and alternator, Ox unbolted and removed the alternator
The fuel and water lines were removed before Ox removed the air intake manifold.
As you can see, there was quite a bit of oil, dirt, and grime accumulated over the 120,736
After the engine mounts were unbolted, Ox guided what was left of the original 5.3L Vortec
The all new GMPP LS327 would borrow most of the original 5.3L external parts to make the e
With the LS327 still in the crate, the orignial engine mounts were lined up and bolted to
After recovering the original 5.3L flexplate, new bolts were given a coat of Permatex Loct
Ox threaded in the original oil pressure switch.
The cylinder head water jacket crossover tube was reused again.
Both original knock sensors and wire connectors were reused.
The new GMPP LS327 engine was almost ready—using the original 5.3L brackets, mounts, flexp
Ox carefully guided the new GMPP LS327 crate engine down into the Avalanche’s engine bay a
Pulleys and alternator bracket was then secured to the engine block.
A 13mm deep socket and 3/8-inch ratchet were used to secure the coil pack rails to the new
New intake manifold gaskets were carefully installed onto the cathedral port intake manifo
Ox used a 10mm socket with a long extension and ratchet to secure the intake manifold to t
After the alternator was installed, Ox relieved the tension on the belt tensioner and slip
Underneath, Ox used a closed wrench to secure the bellhousing bolts.
An airgun was used, with a long extension and a 13mm deep socket, to secure the starter.
The coil/spark plug wires were installed before Ox secured the new exhaust gaskets and ori
Due to rust and contaminates in the original engine water jackets and old aluminum radiato
Once the new radiator was in place, Ox installed the original 5.3L fan onto the water pump
After the fan shroud was installed and secured, the K&N air intake tube and conical air fi
After the new GMPP LS327 crate engine was assembled, Ox then dropped it between the frame
Driving the Avalanche for a few days, it was again secured on the Mustang Dyno and ready
FROM THE DRIVER SEAT
As we drove the Avalanche from the office over to Traders in Santa Fe Springs, we could tell the engine was tired. After the new GMPP LS327/5.3L HO was lowered into the Avalanches engine bay, and everything was plumbed and wired, Ox inserted the key into the ignition, waited a couple seconds and turned the key. The new LS327 fired right up. Despite the engine being pre-run at GMPP before being shipped, Ox ran the engine at 2,000 rpm for about 20 minutes before we took it for a test drive. The new LS327 performed very well on its maiden voyage down the street and a short sprint on the freeway. When the ignition was turned off, the engine shut off tightly. A number of original engine parts were reused on the new GMPP LS327 crate engine and we no problems mating all the parts together.
GM PERFORMANCE PARTS LS327/5.3L HO SPECS
Part Number: 19165628
Engine Type: LS series small-block V-8
Displacement: (cubic inches) 323 (5.3L)
Bore x Stroke: (in) 3.78x3.62
Block: PN 12551360 Cast-iron with six-bolt, cross-bolted iron main caps
Crankshaft: PN 12553480 Nodular iron
Connecting Rods: PN 12568734 Powdered metal steel
Pistons: PN 12571545 Hypereutectic aluminum
Camshaft: PN 12561721 Hydraulic roller
Camshaft lift: (in) .467 intake / .479 exhaust
Camshaft duration: @ .050 in. 196-degrees intake / 201-degress exhaust
Cylinder heads: PN 12559865 Aluminum w/ cathedral ports
Valve sizes: (in) 1.89 intake / 1.55 exhaust
Compression ratio: 9.5:1
Rocker arms: PN 10214664 Investment cast, roller trunnion journals
Rocker arm ratio: 1.7:1
Recommended fuel: 87-octane
Maximum rpm: 6,000
YOUR QUESTIONS ANSWERED
Time Spent Working: 16 hours
Degree of Difficulty: Advanced
Air impact gun, air wrench, sockets, ratchets, assorted sockets, combination wrenches, cleaning solvent, hoist
GM Performance Parts crate engine LS327/5.3L HO PN19165628
Radiator GM SUV PNSAP-2423
Radiator hose lower PNSAP-62261
Radiator hose upper PNSAP-62262
Engine coolant Shell PNSAP-DEXCOL
Engine oil PNRP10/0 Royal Purple $4.00 ea (5)
Engine exhaust manifold gaskets PNSAP-18813
A/C Belt PNSAP-4040377
Engine intake manifold gaskets LS1 PNSAP-230026
Total Cost: $3,523.35
(prices from Traders, Engine Depot and Scoggin-Dickey Parts)